The instant invention relates generally to missile propulsion and more particularly to a duel, side-mounted inlet for ramjet missiles.
The use of the ramjet principle of propulsion in missiles, while effective, presents many problems, particularly the placement of the ram air inlet to obtain high velocity ram air at normally expected flight angles of attack. Rather than use rotary vane air compressors as in conventional jet engines, the ram jet depends on its relative motion with the air stream to gather and compress combustion air.
Previous attempts at obtaining sufficient ram air involved the use of a coaxial duct in the nose cone of the missile and aft-mounted inlet systems having four inlets along the side of the missile in an "+" or ".times." orientation about circumference. While the orientations of these ram inlets provide sufficient performance for the accomplishment of missions wherein the vehicle is subjected to small angles-of-attack, they cannot provide sufficient performance at the high angles-of-attack associated with the trajectory requirement imposed upon a missile engaging a manuevering target. In addition the nose cone duct orientation produced excess drag compared to the conventional ogive nose cone.
In the conventional side-mounted "+" and ".times." orientation, there are four orthogonally opposed inlets about the circumference of the vehicle. These orientations are in reference to the pitch plane and presume that the missile is stabilized in roll. In the aft-mounted inlet systems, both inlet orientation and circumferential location on the vehicle affect the ramjet's angle-of-attack performance, with the "+" configuration providing somewhat superior inlet performance to the ".times." configuration.
The problems encountered with the aft mounted conventional orientations is that the angle-of-attack flow spillage characteristics have an important effect on the ramjet engine performance.
Recent studies of the use of air-breathing (ramjet) propulsion in practical missile applications have indicated substantial performance advantages which permit missions beyond the capability of rocket-powered propulsion systems. A primary problem area in the application of these fixed-geometry, air-breathing propulsion systems is the need for efficient ramjet operation over an extended range of flight conditions, i.e., mach number, angle-of-attack and altitude. This extended range of operation is required so that varied mission profiles and a large portion of the boost acceleration may be effectively flown with the air-breathing propulsion mode. It would be highly desirable to provide capabilities for operation at high angles-of-attack without requiring reduced fuel flow during manuevers so that full propulsion system thrust can be maintained. It is desirable to solve these problems without added engine and inlet complexity, such as variable-geometry components. A dual, side-mounted inlet configuration has been found to solve these problems and is the subject of the instant invention.